The present invention relates to a machine for conveying lumber or logs of wood in wood transformation industries such as sawmills.
In sawmills, lumber and logs of wood need to be conveyed between various stations, some of which are at different levels, implying that the lumber and logs must be lifted from one level to another.
Different types of apparatuses for conveying the logs of wood, whether or not the bark is still present on the log, exist. These apparatuses are also used for dropping the logs of wood one by one on a strap conveyor directed perpendicularly to the conveying direction of the apparatus, in such a way that the logs of wood are positioned end-to-end thereon for feeding a wood transformation machine.
One known type of apparatus for conveying logs of wood comprises an inclined panel, on which are operatively mounted several driving belts, which are positioned laterally. The driving belts have protruding lugs all along their length that are designed and positioned in such a way that a log of wood may be carried on a set of aligned lugs and conveyed upwardly by the motion of the driving belts.
One type of apparatus for conveying lumber is known and used in sawmills, and functions similarly to one of the known types of apparatus for conveying logs of wood previously described. This type of apparatus for conveying lumber may carry one or more pieces of lumber at the same time. At the exit, the lumber is transferred on a strap conveyor directed in parallel to the conveying direction of the apparatus and the pieces of lumber are accumulated side-by-side on the strap conveyor.
Another known type of apparatus for conveying logs of wood is called the xe2x80x9cstep-feederxe2x80x9d. U.S. Pat. Nos. 5,374,157, 3,168,190 and 5,678,681 disclose different apparatuses of the xe2x80x9cstep-feederxe2x80x9d type.
The apparatuses described in U.S. Pat. Nos. 3,168,190 and 5,678,681 have one large staircase with several stairs moving independently, in such a way that two adjacent stairs move up and down oppositely alternately. It results that when a log is carried by one stair moving upwardly, it is transferred to the following stair which just moved downwardly in order to pick up the log and move upwardly to transfer the log to the next upstream stair, and so on.
The apparatus described in U.S. Pat. No. 5,374,157 uses the same principle as the one described in U.S. Pat. Nos. 3,168,190 and 5,678,681, but it uses several staircase-like-structures placed side-by-side. Alternately, each staircase-like-structure moves independently up and down by a predetermined distance. They are divided into two sets: a first set, and a second set being intercalate between the staircase-like-structures of the first set. When the first set of staircase-like-structures moves down, the second set of staircase-like-structures moves up. These movements define an arc of a circle respectively. In operation, a log of wood is carried upwardly by the aligned stairs of one set of staircase-like-structures, while the second set of staircase-like-structures moves down until an aligned stair of this second set picks up the log of wood and carries it upwardly until an upstream aligned stair of the first set of staircase-like-structures picks up the log of wood and moves it upwardly, and so on.
The above-described apparatuses for conveying lumber or logs of wood have many drawbacks. One drawback of these apparatuses is their complex mechanics, which break frequently. The constitutive pieces are subject to wear, and the apparatuses require constant maintenance.
Another drawback is the fact that these apparatuses for conveying lumber or logs are generally noisy. Having less noise means a better working environment and possibly less injuries to the workers due to disturbance.
In the case of the known apparatuses for conveying logs of wood, a further drawback consists in the fact that there exists the possibility of having two logs of wood carried by the apparatus at the same time, which results in transferring two logs side-by-side on the strap conveyor. This is inconvenient since it is necessary to have the logs aligned end-to-end to avoid obstruction of the transformation machine fed by the strap conveyor. The possibility of two logs being carried at the same time is frequently caused by a curved log or a log that still has bark, which rolls to a downstream step and is conveyed together with the downstream log.
Still in the case of the known apparatuses for conveying logs of wood, an additional drawback is their inability to convey the logs of wood at a high speed. Some of the apparatus known in the field cannot convey the logs at a speed higher 55 logs per minute. The fact that a curved log or a log with bark rolls down one step or more in some of the known apparatus, represents an additional factor which slows down the conveying speed.
The present invention is directed to a machine that overcomes one or more of the above-mentioned drawbacks.
In accordance with the present invention, there is provided a machine for conveying elongated wooden pieces. Each wooden piece has a width falling within a given range. The machine comprises:
a frame having two opposite sides, a front and a back, the wooden pieces being conveyed in a conveying direction from the front towards the back of the frame;
at least two parallel conveying shafts rotatably mounted on the frame, and being substantially perpendicular to the conveying direction, each shaft having an axis of rotation;
rotating means for rotating each shaft about said axis of rotation at a desired speed in a direction corresponding to the conveying direction; and
at least two toothed circular plates mounted on each shaft, each plate having a radius and extending in a plane crossing the axis of rotation of the shafts, the plates of a shaft being offset with respect to the plates of an adjacent shaft, each tooth of each plate being spaced apart from an adjacent tooth by a distance which corresponds substantially to the range of diameter of the wooden pieces and defining a space therebetween for receiving at least a portion of a wooden piece, the teeth of the plates mounted on a same shaft being aligned;
wherein each shaft is spaced from an adjacent shaft by a distance at least equal to the radius of a toothed plate.
In accordance with the present invention, there is also provided a machine for conveying logs of wood. Each log of wood has a width falling within a given range. The machine comprises:
a frame having two opposite sides, a front and a back, the logs being conveyed in a conveying direction from the front towards the back of the frame;
at least two parallel conveying shafts rotatably mounted on the frame, and being substantially perpendicular to the conveying direction, each shaft having an axis of rotation;
rotating means for rotating each shaft about said axis of rotation at a desired speed in a direction corresponding to the conveying direction; and
at least two toothed circular plates mounted on each shaft, each plate having a radius and extending in a plane crossing the axis of rotation of the shafts, the plates of a shaft being offset with respect to the plates of an adjacent shaft, each tooth of each plate being spaced apart from an adjacent tooth by a distance which corresponds substantially to the range of diameter of the logs and defining a space therebetween for receiving at least a portion of a log, the teeth of the plates mounted on a same shaft being aligned;
wherein each shaft is spaced from an adjacent shaft by a distance at least equal to the radius of a toothed plate.
In accordance with the present invention, there is further provided a machine for conveying lumber. Each lumber has a width falling within a given range. The machine comprises:
a frame having two opposite sides, a front and a back, the lumber being conveyed in a conveying direction from the front towards the back of the frame;
at least two parallel conveying shafts rotatably mounted on the frame, and being substantially perpendicular to the conveying direction, each shaft having an axis of rotation;
rotating means for rotating each shaft about said axis of rotation at a desired speed in a direction corresponding to the conveying direction; and
at least two toothed circular plates mounted on each shaft, each plate having a radius and extending in a plane crossing the axis of rotation of the shafts, the plates of a shaft being offset with respect to the plates of an adjacent shaft, each tooth of each plate being spaced apart from an adjacent tooth by a distance which corresponds substantially to the range of diameter of the lumber and defining a space therebetween for receiving at least a portion of a lumber, the teeth of the plates mounted on a same shaft being aligned;
wherein each shaft is spaced from an adjacent shaft by a distance at least equal to the radius of a toothed plate.
In accordance with the present invention, there is also further provided a machine for separating and conveying logs of wood where each log has a diameter falling within a given range and the machine comprises:
a frame having two opposite sides, a front and a back, the logs of wood being conveyed in a conveying direction from the front towards the back of the frame;
at least three parallel conveying shafts rotatably mounted on the frame, and being substantially perpendicular to the conveying direction, each conveying shaft having an axis of rotation, all the shafts extending in an inclined plane so that the back of the frame is higher than the front of the frame and the conveying direction is oriented upwardly
rotating means for rotating each shaft about its axis of rotation at a desired speed in a direction corresponding to the conveying direction;
at least two notched circular plates mounted on a most upstream shaft, each notched plate having a circumference being provided with a plurality of thin notches;
at least two toothed circular plates mounted on each shaft being downstream from the most upstream shaft, each tooth being spaced apart from an adjacent tooth by a distance which corresponds substantially to the range of diameter of the logs of wood, and defining a space therebetween for receiving at least a portion of a log, the teeth of the plates mounted on a same shaft being aligned;
a shelf on the front of the frame for receiving a bundle of logs of wood; and
two side walls mounted on each opposite side of the frame and extending upwardly, the walls defining with the shelf a separating and conveying area;
wherein each of the toothed plates and the notched plates has a radius and extends in a plane crossing to the axis of rotation of the shaft on which it is mounted, the plates of a shaft being offset with respect to the plates of an adjacent shaft; and
wherein each shaft is spaced from an adjacent shaft by a distance at least equal to the radius of a toothed plate or the radius of a notched plates.
The invention and its advantages will be better understood upon reading the non restrictive description of the preferred embodiments of the present invention. This description is given with reference to the appended drawings.